Many modern personal computing devices are configured with high-resolution, color liquid crystal displays (LCDs) that can employ a complex matrix (e.g., an active-matrix) of switching thin-film transistors (TFTs) and pixel storage capacitors, vertical and horizontal polarizing filters, color filters, a liquid crystal layer, a light emitting diode (LED) backlight system, etc. As would be understood by those having ordinary skill in display technologies, active-matrix addressed TFT displays typically appear brighter, present sharper images, and exhibit improved response times, as compared to their passive-matrix addressed TFT display counterparts (e.g., passive-matrix displays of a similar size).
Within these active-matrix LCD displays, a specific column line may be charged to illuminate a single display pixel, or multiple display pixels along different row lines, by selectively switching on a TFT(s) associated with a corresponding pixel address(es) (e.g., a pixel addressed to a single row line). When a TFT is switched on, a corresponding pixel storage capacitor may be charged along the column line to twist liquid crystals of the pixel enough to allow light from an LED backlight system to pass through the liquid crystal layer and illuminate the pixel. The color of the illuminated pixel is defined by its applied color filter. In this manner, individual pixels can be illuminated by supplying current, and therefore power, to a particular column line within an LCD display. A display driver or controller may be employed to dynamically manage current flow to each of the column lines within an LCD display and/or to gate TFTs (e.g., turning TFTs on/off) in corresponding row lines.
Unfortunately, one major power drain of LCD displays occurs when images presented at a display are periodically refreshed, in accordance with a live refresh rate (LRR) that may be assigned by a device manufacturer. The default LRR of a device display can be driven by a timing controller entity that is statically configured by a graphics processor unit (GPU), or another designated system-on-chip (SoC) component of a host system, to ensure that a constant LRR is maintained at the display, regardless of what image presentation processes are being performed at the device or what image content is being (or will be) presented at the display. In many different types of personal computing devices the LRR for a device's LCD display is standardized at a refresh rate of 50 or 60 Hertz (Hz). However, with the recent emergence of high-definition (HD) 3-dimentional (3D) display systems, LRRs have increased to 120 Hz and 240 Hz. This trend is expected to continue, such that future display technologies may have LRRs of 300 Hz, or beyond.
The LRR of a device display is proportional to its power consumption; the higher the LRR is for a particular display type the more power that display will consume. As such, device display power consumption is an increasing area of interest for scientists and engineers working in the field of consumer electronics displays. Many portable electronic devices (e.g., laptop computers, tablet computers, mobile phones, electronic book devices, music players, etc.) having a limited, exhaustible battery life, can perform routine display procedures that do not necessitate a LRR equal to or exceeding 50 or 60 Hz. In these scenarios, it would be advantageous to be able to dynamically detect different device states and/or display operations that do not require such a conservative LRR, and then lower a corresponding device's display refresh rate accordingly, to minimize power consumption and extend device mobility.
By way of example, in some situations, a device display may be controlled to present a single image frame that will not change over a known period of time. During this established time interval, the device display may be in what is known as a screen-on-idle mode, which does not require a display screen image refresh action. However, in an effort to prevent a detrimental “screen burn,” and to limit display component degradation, it still may be necessary to refresh a static display screen image during the screen-on-idle mode. As such, it would be beneficial to be able to reduce the refresh rate of a device display to be less than the device's default LRR in many situations, including the scenarios described above. Accordingly, there exists a need for a solution that can dynamically reduce a device's display refresh rate to minimize power consumption, without degrading a user's visual experience. In this regard, it would be desirable to be able to compensate for reduced brightness levels and other visual artifacts that can result from operating a display at reduced refresh rates.